This invention relates to signature machines of the type shown in McCain U.S. Pat. No. 4,241,907. Signatures are folded, printed sheets. A signature machine feeds signatures from individual pockets onto a saddle conveyor to create a book. A stack or pile of signatures is loaded into the infeed hopper of a signature machine. An extractor mechanism withdraws individual signatures one at a time from the front of the stack. The extractor may include pile suckers, an extracting cylinder, a lap cylinder and an opening cylinder, as fully set forth in McCain U.S. Pat. No. 4,241,907, the disclosure of which is incorporated by reference herein. The extractor deposits the signatures on the saddle conveyor.
An infeed conveyor is mounted in the hopper. A ratchet or one way clutch mechanism drives the infeed conveyor to advance signatures toward the front of the pile. This device can be controlled to advance the pile in very small increments, something approaching the thickness of a signature. An infeed governor pin activates the infeed conveyor motion in response to removal of signatures from the pile. This relatively fine control, however, limits the size of the infeed hopper. The mechanism simply is not powerful enough to handle heavy loads on the infeed conveyor.
The infeed hopper must present signatures to the extractor in a loose condition wherein they are free to settle down and get picked up by the pile suckers. To this end, the infeed hopper has side guides which are angled inwardly to hold back the pile and take excessive pressure off the signatures near the stockplate. But to whatever degree the side guides hold back the pile, the condition of the signatures at the front of the pile will be affected by the pressure of signatures near the back of the pile. The ideal condition results from uniform pressure. The side guides can be adjusted to provide the correct resistance to the pile if the pressure is uniform. However, uniform pressure cannot be ideally attained by hand loading of the hopper. Variable pressure inevitably results as the infeed goes from full to partially empty
The problems of hand loading are further compounded by the size limitations of the infeed hopper. Since the hopper cannot be made very large, an operator must frequently reload it to achieve the desired uniform pressure. A more likely scenario is that the hopper will not get constant attention and the extractor will operate under less than ideal conditions. The swing-up loader of the present invention solves these problems by maintaining a uniform stack or pile in the infeed hopper of the signature feeder.